Small marine vessels and the like are provided with radar reflectors for preventing maritime disaster, and particularly, in congested sea areas, nighttime navigation, under poor weather conditions such as fog and so forth, it is the duty of such marine vessels to sail with radar reflectors mounted.
Regarding conventional radar reflectors, so-called all-directional corner reflectors capable of catching radar waves from all directions are used, such being comprised of eight triangular corner reflectors, each of these comprised of three orthogonal faces of metal plates.
However, since such all-directional corner reflectors are not capable of being folded, the corner reflector is stored in a state of the three faces of metal plates remaining in an orthogonal state, i.e., in a three-dimensional state.
As a result, a greater storage space is required therefore as compared to cases wherein the corner reflector is folded and stored, and also, care must be taken so as not to crush the metal plates.
Therefore, a foldable reflector (radar reflector) such as described below has been developed (See Japanese Unexamined Utility Model Publication No. 62-80412). That is to say,
a radar reflector of a spherical outer form comprising: eight corner reflectors of which each corner is formed of three planes, wherein five main reflector plates are bound in a booklet-like manner, and sub-reflector plates which have an apex angle of 90.degree. and which are foldable in two along the bisector of the apex angle are each provided between the respective five main reflector plates, and wherein the sub-reflector plates are positioned with the apex angle thereof at the ridge of each of the main reflector plates and are integrally fixed upon the central bisectors of the main reflector plates on both sides of the apex angle, and wherein the main reflector plates on both right and left sides are provided with mutually overlapping through holes at a position at 45.degree. from the ridge and also a fastener is provided thereto so as to allow for overlapping adhesion at each of the outer planes, thus constructing a radar reflector which is assembled by opening the main reflector plates in a cross-like intersecting manner with the ridge serving as the axis.
As it can be understood from the form thereof, all-directional corner reflectors are limited regarding the angles of incidence and reflection of radar waves, and have approximately the same angle of reflection in both the horizontal and longitudinal directions with isosceles triangle corner reflectors.
Accordingly, the greatest angle of reflection at the width of approximately 40.degree. (-3 dB half-voltage value) is 36.degree. upwards when the triangle serving as the base (bottom reflector plate) is placed flat, so in the event that the reflector is to be mounted, the mounting thereof must be conducted such that the reflector plate is 36.degree. upwards. This upwards angle is referred to as a detection design angle.
However, radar reflectors according to the conventional example are assembled, then strings are attached to the through holes in the main reflector plates, and the radar reflector is hung by means of fixing the strings to predetermined locations, and accordingly, in the event that the radar reflector is subjected to exterior force such as the wind, the reflector is displaced at random in up and down directions, forward and backward directions, right and left directions, and so forth, so that it is difficult to maintain the bottom reflector plate at the detection design angle. Consequently, radar waves cannot be caught and reflected effectively over a wide area.
The object of the present invention is to provide a foldable handy reflector which can be set at the detection design angle in a precise and yet easy manner.